Gantry mill free from the effects of thermal deformation of a bridge member

ABSTRACT

A gantry mill free, from the effects of thermal deformation of a bridge member, comprises a pair of combinations each consisting of a base member, a bed member on which the base member can travel and which is fixed provided with a driving strip member directed in the direction of travel of the base member, and a driving device engaged with the driving strip member. A bridge member is connected between the head portions of the base members. In one combination, the base member and the driving device are fixed to each other and the bed and base members are constrained against relative lateral displacement and relative vertical displacement while being capable of relative longitudinal displacement while being capable of relative longitudinal displacement in the direction of travel. In the other combination, the base member and the driving device are constrained against relative longitudinal displacement and relative vertical displacement, but are capable of relative lateral displacement through a distance in excess of the maximum thermal deformation of the bridge member. Also, the bed member and the base member in the other combination are constrained against relative displacement in the vertical direction but are capable of relative displacement in the lateral direction through a distance in excess of the magnitude of thermal deformation of the bridge member, and are also capable of relative displacement in the travel direction, with the bed member and the driving device being constrained against relative displacement in the lateral direction. The bed members are fixedly mounted in spaced parallel relation, and the base members are conjointly movable, in fixed parallel relation, longitudinally of the bed members.

Unite States Patent [191 Kitainura et a1.

[ net. 25, ran

[75] Inventors: Tetsuo Kitamura; Akira Tamai,

both of Hiroshima-ken, Japan [73] Assignee: Mitsubishi Jukogyo Kabushiki Kaisha, Tokyo, Japan [22] Filed: Mar. 10, 1972 [21] Appl. No.: 233,689

Primary Examiner-Andrew R. Juhasz Assistant ExaminerZ. R. Bilinsky Att0rney.lohn J. McGlew et al.

[57] ABSTRACT A gantry mill free, from the effects of thermal deformation of a bridge member, comprises a pair of combinations each consisting of a base member, a bed member on which the base member can travel and which is fixed provided with a driving strip member directed in the direction of travel of the base member, and a driving device engaged with the driving strip member. A bridge member is connected between the head portions of the base members.

In one combination, the base member and the driving device are fixed to each other and the bed and base members are constrained against relative lateral displacement and relative vertical displacement while being capable of relative longitudinal displacement while being capable of relative longitudinal displacement in the direction of travel. In the other combination, the base member and the driving device are constrained against relative longitudinal displacement and relative vertical displacement, but are capable of relative lateral displacement through a distance in excess of the maximum thermal deformation of the bridge member. Also, the bed member and the base member in the other combination are constrained against relative displacement in the vertical direction but are capable of relative displacement in the lateral direction through a distance in excess of the magnitude of thermal deformation of the bridge member, and are also capable of relative displacement in the travel direction, with the bed member and the driving device being constrained against relative displacement in the lateral direction. The bed members are fixedly mounted in spaced parallel relation, and the base members are conjointly movable, in fixed parallel relation, longitudinally of the bed members.

6 Claims, 6 Drawing Figures PATENTED 3.780.619

SHEET 2- Bi 4 PATENTED UEC25 I973 SHEU 3 BF 4 mOE GANTRY MHLL FREE FROM THE EFFECTS OF THERMAL DEFORMATION OF A BRIDGE MEMBER FIELD AND BACKGROUND OF THE INVENTION and which may introduce a considerable change in size due to the extremely large-scaled design of the gantry mills, would result in undesirable effects such as seizure at the portions where two members to be relatively displaced make contact with each other such as, for example, at the sliding surfaces between a guide channel and a guide projection or at the engaging portions between a driving worm and a corresponding worm rack.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a novel structure of gantry mill which obviates the above-mentioned disadvantage in the prior art gantry mills and which is designed so that the performance of the gantry mill is not affected by thermal deformation of the bridge member.

According to the present invention, there is provided a gantry mill, free from the effect of thermal deformation of a bridge member, comprising a pair of combinations each consisting of a base member, a bed member on which the base member can travel and which is fixedly provided with a driving strip member directed in the direction of travel of the base members, and a driving device engaged with the driving strip member. A bridge member is connected between the head portions of the base members, the bed members are fixedly interconnected for conjoint displacement in parallel relation to each other in the travel direction along the base members. In one of the combinations, the base member and driving device are fixed connected to each other, and the bed member and base member are constrained against relative displacement in the lateral direction, at right angles to the direction of travel, and in the vertical direction, but are free for relative displacement in the travel direction of the base members. In the other combination, the base member and the driving device are constrained against relative displacement in the travel direction of the base members as well as in the vertical direction, but are free for relative displacement in the lateral direction through a distance in excess of the magnitude of thermal deformation of the bridge member, which is the difference between the maximum and minimum lengths of the bridge member, longitudinally thereof, caused by thermal deformation. Also, the bed member and the base member are constrained against relative displacement in the vertical direction but are free for relative displacement in the lateral direction in excess of the amount of thermal deformation of the bridge member and are also free for relative displacement in the travel direction. The bed memher and the driving device are constrained against relative displacement in the lateral direction.

BRIEF DESCRIPTION OF THE DRAWINGS These and other features and advantages will become apparent from perusal of the following description of its preferred embodiment taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a perspective view of a gantry mill;

FIGS. 2 and 3 are front elevation views of two different prior art gantry mills;

FIG. 4 is a front elevation view, partly in section, of a gantry mill embodying the invention;

FIG. 5 is an enlarged sectional view of the essential parts on the right side as viewed in FIG. 4; and

FIG. 6 is a plan view of the essential parts of the gantry mill embodying the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT As shown in FIG. 1 of the drawings, generally a gantry mill (planomatic) is a traveling bridge type of complex complexed working machine, in which two base members 52 are adapted to travel, respectively, on bed members 51 fixedly mounted parallel to each other, and a bridge member 53 is connected between the head portions of base members 52, and in which a predetermined working is applied to a workpiece through a mannual operation or a numerically controlled auto matic operation, by cooperative actions of a milling bed 54 or the like, which is provided on the bridge 53 so as to move in the lateral and vertical directions, and a floor surface plate 55 or the like provided between the two bed members 5i.

As a bridge feed driving system for the gantry mill, there is advantageously used a combination of a worm and a worm rack. At present, however, gantry mills are extremely large-scaled,so that there were distinctive disadvantages that the thermal deformation of the bridge member 53 caused by the atmospheric temperature variation (Assuming that the length of the bridge is 10m and the temperature difference between summer and winter is 30C., the amount of thermal deformation of the bridge would be about 3mm.) will result in misalignment between the worm and the worm rack, or thermal distortion throughout the machine, and thereby the respective sliding surfaces would be subjected to seizure. In the prior art, there was no gantry mill which was free from such disadvantages. For instance, in the prior art gantry mill as shown in FIG. 2, a pair of fixed bed members 51 and a pair of base members 52 are constrained in relative position, so as to inhibit their relative displacement in the vertical and lateral directions, by means of narrow guides 58, in order to prevent misalignment between the worm 56 and the worm rack 57. However, as a result of the thermal deformation of the bridge member 53, the narrow guides 58 of the respective bed members 51 are subjected to a large force, which causes seizure with the base members 52, and the effect of the thermal deformation is effective throughout the machine, so that the working accuracy cannot be maintained. Also in the prior art gantry mill as shown in FIG. 3, a narrow guide similar to that shown in FIG. 2 is provided only in the bed member 51 on the left side as viewed in FIG. 3, and the bed member 5i and the base member 52 on the other side are free for relative displacement in the lateral direction. However, as a result of the thermal deformation of the bridge member 53, misalignment occurs between the worm 56 and the worm rack 57 on the unconstrained side, which also causes seizure.

Now the essential features of the present invention in contrast to the above-mentioned prior art will be described in more detail with reference to one preferred embodiment as illustrated in FIGS. 4, 5 and 6. in these figures, a lefthand assembly includes bed member 1, narrow guides 2, a lefthand base member at 3, a gib at 4, clamp plates 5, a lefthand feed worm gear box at 6, bolts 7, and a worm rack at 8, spacers at 9, a worm at 10. The righthand bed member at l 1, a righthand base member at 12, a bridge member 13, clamp plates at 14, a righthand feed worm gear box 15, a worm rack at 16, a central guide channel 17, gibs at 18, clamp plates at 19, bolts at 20, spacers 21, a worm 22, bolts at 23, pins 24, a stopper 25, a liner at 26, bolts at 27, a stopper 28, bolts 29, pins at 30, a liner at 31, bolts 32,. a gib 33, bolts 34, a spacer 35, and projections 36. Ari upwardly concave surface of the righthand base 12 is shown at 37, and projections at 38.

Among a pair of combinations each consisting of a base member, a bed member and a feed worm gear box, one combination is designated by A and the other combination is designated by B.

In combination A, the lefthand base member 3 travels on the lefthand bed member 1. On the upper surface of the bed member 1 there is integrally secured worm rack 8 directed in the direction of travel of the base member. The worm 10 is engaged with worm rack 8 and feed worm gear box 6 accommodates worm 10. Base member 3 and worm gear box 6 are fixedly interconnected by bolts 7, with spacers 9 interposed therebetween. The narrow guide 2 is formed integrally with bed member 1, and against Its, upper, lower, left and right surfaces there abut base member 3, gib 4 fixedly connected therewith, and clamp plate 5, so that lefthand bed member 1 and lefthand base member 3 are constrained in relative position so as to inhibit their relative displacement in the lateral and vertical directions (The gib is used for adjusting the gap clearance). The lefthand bed member 1 and the lefthand base member 3 are not constrained in relative position with respect to their relative displacement in the direction of travelling of the base member, and so they are free for relative displacement in such travel direction.

In combination B, righthand base member 12 travels on righthand bed member 11. On the upper surface of bed member 11 there is provided central guide channel 17, within which is fixed the worm rack 16 engaged by worm 22. The worm 22 is subjected to the same rotational motion as the worm 10, so that the lefthand and righthand base members can travel synchronously. The righthand feed worm gear box accommodates worm 22, and is provided with projections 36, which are formed integrally with gear box 15 and project therefrom in both the left and right directions while extending in the direction of travel of the base member. On the opposite ends of the projections 36, considered in the direction of travel of the base members, there are fixedly secured liners 26 and 31, respectively, by means of bolts 27 and 32 (The liners have been quenched in orderto prevent seizure). On the upwardly concave surface 37 of base there 12 are fixedly secured stoppers 25 and 28 by means of bolts 23 and 29 and pins 24 and 30. These stoppers 25 and 28 abut against the end surfaces, considered in the direction of travel of the base members, of liners 26 and 31, respectively. The gib 33 is fastened to stopper 28, with spacer 35 interposed by bolts 34, and due to its inclined surface gib 33 causes a contact pressure between stoppers 25 and 28 and liners 26 and 31. Thus the righthand base member 12 and the righthand feed worm gear box 15 are constrained in relative position so as to inhibit their relative displacement in the direction of travel of the base members. The above-described constraint in relative position, in the direction of travel of the base members, is applied to only one side of righthand feed worm gear box 15 as shown in FIG. 6, and thereby, even if the lefthand and righthand base members were to be displaced relative to each other, the righthand feed worm gear box 15 would not be subjected to detrimental forces. On base member 12 there are fixedly secured clamp plates 19 by bolts 20, and on upwardly concave surface 37 there are fixedly secured spacers 21. The projections 36 of feed worm gear box 15 abut against the lower surfaces of clamp plates 19 and the upper surfaces of spacers 21. in this way, righthand base member 12 and righthand feed worm gear box 15 are constrained in relative position so as to inhibit their relative displacement in the vertical direction. The righthand feed worm gear box 15 and the righthand base member 12 retain therebetween a gap clearance, in the lateral direction, larger than the amount of thermal deformation t of the bridge member (in FIG. 4, the position of righthand base member 12 when it has been subjected tothe thermal deformation of e, is shown by a doubledot chain line), and thereby relative displacement, in the lateral direction, of members .15 and 12, due to thermal deformation of the bridge member, is allowed.

Against the upper and lower surfaces of projections 38 of the righthand bed member 11, abut base member 12 or clamp plates 14 fixedly connected thereto, whereby the righthand bd member 11 and the righthand base member 12 may be constrained in relative position so as to inhibit their relative displacement in the vertical direction. The righthand bed member 11 and the righthand base member 12 retain therebetween a gap clearance, in the lateral direction, larger than the amount of thermal deformation e of the bridge member, and thereby relative displacement, in the lateral direction, of members 11 and 12, due to the thermal deformation of the bridge member, is allowed. The righthand bed member 1 1 and the righthand base member 12 are not constrained in relative position with respect to relative displacement in the direction of travel of the base members, and so they are free for relative displacement in the travel direction.

The righthand bed member 11 and righthand feed worm gear box 15 abut against each other via two gibs 18, and thereby they are constrained in relative position so as to inhibit their relative displacement in the lateral direction. In addition, bridge member 13 connects the head portions of lefthand base member 3 and righthand base member 12. The lefthand bed member 1 and the righthand bed member 11 are fixedly mounted in parallel to each other and to the direction of travel of the base members. The bridge member 13 may be provided with an appropriate working machine.

When the novel structure of a gantry mill according to the present invention is employed, even if the bridge member is subjected to thermal deformation, the alignment between the worm and the worm rack is maintained regularly, no thermal distortion is effective in any part of the gantry mill, seizure between the respective sliding surfaces is prevented, the bridge member can freely travel on the bed members in accordance with the driving by the worms and worm racks and the base members are not subjected to vertical motion, such as vertical vibration with respect to the bed members, and thus a high working precision can be maintained without deteriorating the performance of the gantry mill. The above-described effects and advantages of the present invention are the more useful as gantry mills are increased in size.

What is claimed is:

1. In a gantry mill including a pair of relatively elongated, substantially parallel, laterally spaced bed members, a pair of base members, each mounted on a respective bed member, the base members being conjointly movable, in parallel relation, longitudinally of the bed members, a bridge interconnecting and supported by the base members, and driving means operable to displace the base members and the bridge in a travel direction along the bed members: an improved construction, free from the effects of thermal expansion of said bridge member, comprising first and second combinations each including a respective bed member, the associated base member, a driving strip member on the respective bed member aligned with the travel direction, and a driving device on the associated base member engaged with said driving strip member, the driving strip members and driving devices constituting said driving means; means fixing the base member and driving device of said first combination against relative displacement; means restraining the bed member and base member of said first combination against relative displacement laterally of the travel direction and against relative displacement in the vertical direction, while providing for relative displacement thereof in the travel direction of the base members; and means restraining the base member and driving device of said 1 second combination against relative displacement in the travel direction of the base member and against relative displacement in the vertical direction, while providing for relative displacement thereof in the lateral direction at right angles to the travel direction.

2. in a gantry mill, an improved construction as claimed in claim 1, in which the relative displacement of the base member and driving device of said second combination in the lateral direction is an excess of the magnitude of maximum thermal deformation of said bridge member in a direction longitudinally of said bridge member.

3. In a gantry mill, an improved construction, as claimed in claim 2, including means restraining the bed member and base member of said second combination against relative displacement in the vertical direction while providing for relative displacement thereof in the lateral direction at right angles to the travel direction of said base members.

4. In a gantry mill, an improved construction, as claimed in claim 3, in which said bed member and said base member of said second combination are relatively displaceable in the lateral direction through a distance in excess of the maximum thermal deformation of said bridge member longitudinally of said bridge member.

5. In a gantry mill, an improved construction, as claimed in claim 4, in which the bed member and the base member of said second combination are relatively displaceable in the direction of travel of said base members.

6. In a gantry mill, an improved construction, as claimed in claim 5, including means restraining the bed member and driving device of said second combination against relative displacement in a lateral direction at right angles to the travel direction of said base members. 

1. In a gantry mill including a pair of relatively elongated, substantially parallel, laterally spaced bed members, a pair of base members, each mounted on a respective bed member, the base members being conjointly movable, in parallel relation, longitudinally of the bed members, a bridge interconnecting and supported by the base members, and driving means operable to displace the base members and the bridge in a travel direction along the bed members: an improved construction, free from the effects of thermal expansion of said bridge member, comprising first and second combinations each including a respective bed member, the associated base member, a driving strip member on the respective bed member aligned with the travel direction, and a driving device on the associated base member engaged with said driving strip member, the driving strip members and driving devices constituting said driving means; means fixing the base member and driving device of said first combination against relative displacement; means restraining the bed member and base member of said first combination against relative displacement laterally of the travel direction and against relative displacement in the vertical direction, while providing for relative displacement thereof in the travel direction of the base members; and means restraining the base member and driving device of said second combination against relative displacement in the travel direction of the base member and against relative displacement in the vertical direction, while providing for relative displacement thereof in the lateral direction at right angles to the travel direction.
 2. In a gantry mill, an improved construction as claimed in claim 1, in which the relative displacement of the base member and driving device of said second combination in the lateral direction is an excess of the magnitude of maximum thermal deformation of said bridge member in a direction longitudinally of said bridge member.
 3. In a gantry mill, an improved construction, as claimed in claim 2, including means restraining the bed member and base member of said second combination against relative displacement in the vertical direction while providing for relative displacement thereof in the lateral direction at right angles to the travel direction of said base members.
 4. In a gantry mill, an improved construction, as claimed in claim 3, in which said bed member and said base member of said second combination are relatively displaceable in the lateral direction through a distance in excess of the maximum thermal deformation of said bridge member longitudinally of said bridge member.
 5. In a gantry mill, an improved construction, as claimed in claim 4, in which the bed member and the base member of said second combination are relatively displaceable in the direction of travel of said base members.
 6. In a gantry mill, an improved construction, as claimed in claim 5, including means restraining the bed member and driving device of said second combination against relative displacement in a lateral direction at right angles to the travel direction of said base members. 